avr and due have same config values, so that works. But pins and some values like double stepper frequency should be different to make use of the faster cpu. Our config tool does this.
ui pins depend not only on the board but also on the lcd controller and they even differ in the data needed. Some have spi some 4 bit parallel data. Some have 1 key, others 2 or more. That is why we have them in ui.h sorted by controller and then also with board switches. I'd like to have one set pe rboard but that is not how it works in reality.
